U.S. Pat. No. 3,254,828, issued Jun. 7, 1966, to Hershey Lerner under the title Flexible Container Strips is directed to so called bags on a roll (here the AutoBag patent). This patent discloses a web of bags interconnected by lines of weakness, preferably in the form of perforations, with each of the bags being open on one face. In use the bags are sequentially fed to a loading station. When at the loading station, each bag is blown open, a product is inserted and thereafter separated from the web and, if desired, the bag is then sealed to form a package.
These container strips in the form of chains of pre-opened bags are supplied either on a roll as taught in the AutoBag patent or festooned in a carton in the manner taught in U.S. Pat. No. 4,201,029, issued May 6, 1980, to Bernard Lerner et al. under the title Method and Apparatus for Packaging, (here the Wig-Wag patent). Such container strips have been sold by Automated Packaging Systems, Inc. of Streetsboro, Ohio, the assignee of the present case, under the trademark AutoBag and have enjoyed great commercial success.
Both AutoBag and competitive products have usually been made by feeding a tube through a converting machine. Such a machine forms transverse seals to delineate the bottoms of the bags and transverse lines of weakness by perforating both layers of the tube to delineate contiguous ends of adjacent bags. After the perforations are formed, a "zinging" operation is performed on each bag to open the front of the bag while leaving the perforations of the back intact.
Relatively recently a market has developed for these chains of bags made from two layers of plastic, so that the plastic of the front of the bag is different from that of the back of the bag. For example, some customers for such bags may wish the back of the bag to be white to enhance the legibility of information imprinted on it such as instructions on how to use a product packaged in the bag. The front of the bag is clear, so that the contents of a package are readily visible. To accomplish this two single layer webs of plastic are fed from respective supplies in a manner similar to that taught in U.S. Pat. No. 4,337,058 issued Jun. 29, 1982 to Bernard Lerner under the title Method of Making a Container Strip Having Inserts. Marginal edges of the two webs are then fused together to form a tube and remainder of the container strip manufacture is identical to that when the supplied work piece is a flattened tube.
So called "multiple up" production has also become quite customary. With multiple up, the work piece may be either a relatively wide flattened tube or two relatively wide single ply sheets fed together and fused. In either event hot knives are used to sever the work piece into two or more elongate tubes and thereafter each new tube is made into a chain of pre-opened bags.
When bags are made from two single ply webs, every effort has been made to provide identical tension on the two webs, so that once made into a tube the only difference of the tube from one provided as a tubular work piece is that the front and back are not identical, such as the back may be pigmented while the front is clear. With the two single ply approach, if the bag making machine was not adjusted properly, once opened the bags would not lie flat with the separated edges which delineate the openings lying in closely juxtaposed positions. The resultant product was often scrap. If the edges were not juxtaposed but rather there was a gap between them, they were rejected because they were perceived to be unacceptable to customers as unsightly and bags which would produce packages with misaligned top edges. If the top edge of an opened bag overlapped the bottom of the adjacent bag, all too often the spark gap detector used for bag registration in a bagging machine would not function properly. Such a bagging machine is disclosed in U.S. Pat. No. 4,014,154, issued Mar. 29, 1977, to Bernard Lerner and related patents identified therein (here the H-100 patents).